1. Field of the Invention
The present invention is concerned with methods for application of liquid treating agents to the inner surfaces of well casings. More particularly, the invention is concerned with such methods which substantially inhibit or prevent passage of the treating agents into the well production zones, while at the same time creating a substantially uniform film of treating agent on the inner casing surfaces. The invention is particularly suited for application of film-type corrosion inhibitors to the inside surfaces of well casings.
2. Description of the Prior Art
During the production of oil and gas, water (or brine) is typically produced as an undesirable byproduct. When brine is generated in the presence of carbon dioxide, carbonic acid species may occur in solution resulting in greater water production and increased corrosion problems. In order to prevent failures due to corrosive metal losses, corrosion-inhibiting chemicals are frequently introduced into producing or injecting wells.
There are several methods for applying corrosion-inhibiting chemicals to protect downhole metal goods. The corrosion inhibitor may be supplied as a free-flowing liquid, as water or oil external emulsions, or as solids Inhibiting chemicals may be applied intermittently or continuously into a given well. In continuous applications, a liquid inhibitor is injected into the well casing. In many batch applications, corrosion inhibitor is injected and flows down the casing followed by a liquid flush.
A problem often encountered in application of corrosion inhibitors is that the inhibitors may adversely affect well production. It is believed that this problem stems from the tendency of corrosion inhibitors to flow into the production zone of the well and adhere to the production structure, particularly in the case of film-forming inhibitors.
There is accordingly a need in the art for an improved method of well treating agents such as corrosion inhibitors into producing wells, without the attendant problem of retarding oil or gas production.